1. Field of the Invention
The present invention relates to systems and methods for controlling an on-board emissions treatment system of a vehicle.
2. Background Art
Manufacturers of vehicles and internal combustion engines used in a variety of diverse applications are continually striving to improve engine/vehicle fuel economy and performance while reducing emissions. Effective emission control strategies often include control of the combustion event in addition to various devices that treat the exhaust before it reaches the atmosphere. Various types of emission control systems introduce one or more substances directly or indirectly to the engine via the fuel supply, air/fuel intake, exhaust, or directly to an engine cylinder or emissions control device, such as a catalyst. For example, substances acting as reducing agents or reductants, such as aqueous urea or hydrocarbons (other than fuel) may be used in lean air/fuel ratio engine applications including diesel engines in combination with lean NOx catalysts (or selective catalytic reduction (SCR)) to treat nitrous oxide feedgas emissions. These substances generally require a storage and distribution system separate from the primary fuel storage and distribution system that must accommodate physical properties different from the primary fuel, such as being more vulnerable to freezing, for example.
Appropriate positioning of the emissions treatment substance storage reservoir and distribution system next to heat rejecting elements of the engine/vehicle, or an active heating element or device, may be required to assure proper operation of the emissions treatment system in extreme environments. However, due to the combustibility of the primary fuel and/or fuel vapor, these approaches may be problematic in applications where the emissions treatment system and primary fuel supply share a common space. For example, U.S. Pat. Nos. 6,554,031 and 6,216,755 disclose a dispensing system that may be used to simultaneously supply a primary fuel and an emissions treatment substance through an integrated nozzle to respective supply tubes integrated within a common fill tube or pipe of a vehicle. This process, which may also be referred to as co-fueling, is one example of an application where a portion of the emissions treatment substance system may be susceptible to freezing, and is not amenable to direct heating due to the presence of primary fuel and fuel vapor.